The isolation of Staphylococcus aureus tea tree oil-reduced susceptibility mutants

Phytother Res. 2014 Aug;28(8):1240-5. doi: 10.1002/ptr.5123. Epub 2014 Feb 12.


Tea tree oil (TTO)-reduced susceptibility (TTORS) mutants of two Staphylococcus aureus laboratory strains were isolated utilizing TTO gradient plates. Attempts to isolate TTORS mutants employing agar plates containing single TTO concentrations failed. All TTORS mutants demonstrated a small colony variant (SCV) phenotype and produced cells with a smaller diameter, as determined by scanning electron microscopy. The addition of SCV auxotrophic supplements to media did not lead to an increase in TTORS mutant colony size. Revertants were also isolated from the TTORS mutants following growth in drug-free media, and all revertant strains demonstrated phenotypes similar to their respective parent strains. Transmission electron microscopy revealed that an SH1000 TTORS mutant demonstrated a thinner cell wall and novel septal invaginations compared with parent strain SH1000. In addition, comparative genomic sequencing did not reveal any mutations in an SH1000 TTORS mutant previously linked to well-characterized SCV genotypes. This study demonstrates that TTO can select for a unique SCV phenotype.

Keywords: Staphylococcus aureus; electron microscopy; genomics; reduced susceptibility; small colony variants; tea tree oil.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Culture Media / chemistry
  • DNA Mutational Analysis
  • Genotype
  • Microbial Sensitivity Tests
  • Microscopy, Electron, Scanning
  • Microscopy, Electron, Transmission
  • Mutation
  • Phenotype
  • Staphylococcus aureus / drug effects
  • Staphylococcus aureus / genetics
  • Staphylococcus aureus / isolation & purification*
  • Staphylococcus aureus / ultrastructure
  • Tea Tree Oil / pharmacology*


  • Culture Media
  • Tea Tree Oil